Hi, All,
Is my understanding correct?
On Sat, Aug 20, 2016 at 01:40:13AM +0000, Wei Yang wrote:
>The (start, size) tuple represents a range [start, start + size - 1],
>which means "start" and "start + size - 1" should be compared to see
>whether the range overflows.
>
>For example, a range with (start, size)
>
> (0xffffffff fffffff0, 0x00000000 00000010)
>
>represents
>
> [0xffffffff fffffff0, 0xffffffff ffffffff]
>
>would be judged overflow in the original code, while actually it is not.
>
>This patch fixes this and makes sure it still works when size is zero.
>
>Signed-off-by: Wei Yang <richard.weiy...@gmail.com>
>---
> arch/x86/kernel/e820.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
>diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
>index 621b501..871f186 100644
>--- a/arch/x86/kernel/e820.c
>+++ b/arch/x86/kernel/e820.c
>@@ -388,11 +388,11 @@ static int __init __append_e820_map(struct e820entry
>*biosmap, int nr_map)
> while (nr_map) {
> u64 start = biosmap->addr;
> u64 size = biosmap->size;
>- u64 end = start + size;
>+ u64 end = start + size - 1;
> u32 type = biosmap->type;
>
> /* Overflow in 64 bits? Ignore the memory map. */
>- if (start > end)
>+ if (start > end && likely(size))
> return -1;
>
> e820_add_region(start, size, type);
>--
>1.7.9.5
--
Wei Yang
Help you, Help me
